Noise-induced hearing loss (NIHL) continues to be one of the most common occupational disorders, even in OSHA compliant workplaces. Prevention of occupational hearing loss is a top priority of the National Occupational Research Agenda (NORA). This proposal is to continue the Daily Exposure Monitoring of Noise (DEMON) Study, a study of a unique intervention to prevent NIHL by use of an innovative technology (QuietDose) that records noise exposure levels inside of hearing protection on a continuous basis. In the first phase of the study, intervention subjects and controls have been recruited and regular downloading of noise exposures is occurring. The second phase of the DEMON study will continue to follow this unique cohort in order to determine the effectiveness of the intervention (in both a mandatory and voluntary use setting), better understand the dose response relationship between noise exposure and hearing loss (including the role of impulsive noise) and also compare the effective attenuation of hearing protection over time with fit tests done at a single point in time. PUBLIC HEALTH RELEVANCE: This research studies an innovative technology that may overcome critical barriers to the effective prevention of noise induced hearing loss including the problem of assessing the true noise exposures that workers are receiving, (how to assess the actual fit and performance of hearing protectors), understanding the damage risk relationship between noise exposure and hearing loss, (including the impact of impulsive noise exposures), and the problem of assessing the effectiveness of interventions to prevent hearing loss. In addition, it will use the unique opportunity of a worker cohort whose true occupational noise exposure can be determined on an individual level to explore the critical questions of delayed effects of noise on hearing loss. The results of this study could have major research to practice (r2p) implications for hearing conservation, creating important new opportunities for the prevention of noise-induced hearing loss.